| Mount Simon Sandstone | |
|---|---|
| Stratigraphic range: | |
| Type | Geological formation |
| Unit of | Potsdam Sandstone |
| Underlies | Eau Claire Formation and Rome Formation |
| Overlies | Hinckley Sandstone and Middle Run Formation |
| Thickness | up to 2,000 feet (610 m) |
| Lithology | |
| Primary | Coarse sandstones |
| Other | Occasional fine dark grey or maroon shales |
| Location | |
| Extent | Illinois, Indiana, Kentucky, Michigan, Minnesota, Ohio, and Wisconsin, |
| Type section | |
| Named for | Mount Simon escarpment in Eau Claire County, Wisconsin [1] |
| Named by | E. O. Ulrich |
| Thickness at type section | 235 feet |
The Mount Simon Sandstone is an Upper Cambrian sandstone and is found in many states in the Midwest such as Wisconsin, Minnesota, Iowa, Illinois, Iowa, and Missouri.
The Mount Simon formation is the equivalent of the La Motte Sandstone formation in the St. Francois Mountains of Missouri. [1].It was deposited in a nearshore environment, unconformably overlying Precambrian basement, and underlying the Eau Claire Formation in Wisconsin. [2]
The Mount Simon sandstone is named after an escarpment of sandstone in Eau Claire Wisconsin called the Mount Simon by E.O. Ulrich. [1]
Geology
The Mount Simon sandstone is composed of three main lithofacies. First, the lower Mount Simon is composed of a medium to coarse gained sandstone, which is interpreted to have a diagenesis of a high-energy river system. [3]
The middle Mount Simon is a fine to medium grained sandstone with shale beds in it, this is interpreted to be in a high-energy delta. [4]
Finally, the upper Mount Simon is a sandstone that is interpreted to be deposited in a sand shoal or a tidal flat deposits. The upper Mount Simon also has fossil content such as brachiopod shells that are broken up. [4]
There are also different lithofacies within the Mount Simon, which include siltstones, mudstones, and conglomerates. The mudstone and siltstone range from 8cm to 1m and is gray to green-gray, however dominantly red. There are also some interbedded layers of small sand grains. The mudstone and siltstone layer is interpreted to be deposited in a distal braid plain ( braided river). [5]
The conglomerate layer consists of quartz pebble (1-2cm with a maximum of 3-4cm) conglomerates and are well to poorly sorted. The conglomerate layer is at the basal scour of the bed and is 2.5-13cm thick. This layer is interpreted to be deposited in a medial braid plain and the conglomerate is a result of fluctuations in the energy of the river. [5]
Accessory Minerals
There are other minerals that are included in the Mount Simon other than quartz grains. Zircon is the most abundant non-opaque mineral in the sandstone, and they range in length with the average being .1-.2mm. The color of the zircons was colorless to pink, and some were oxidized, leaving a reddish-orange to yellow color. The next most abundant mineral is tourmaline, which ranged between .15 to .3mm, and the vast majority of the grains were green to yellow-brown, and the minority were blue, pink, green, and violet colors. Rutile was the next most abundant mineral, ranging between .1-.2mm in size, and was a yellow-brown or red color. Garnet was the next most abundant and is colorless to pinkish-brown, and ranged in size between .1-.3mm. Apatite, Amphibole, Pyroxene, Epidote, Diaspore, Staurolite, and Anatase are all minerals that occur in the sandstone however, they are not very abundant and only take up a small percent of the grains in the rock. [6]
References
- ^ a b c "Mount Simon Sandstone". Indiana Geological & Water Survey. Retrieved 2024-04-08.
- ^ Hamblin, A. P. (2011). Detailed outcrop and core measured sections of Upper Cambrian and Middle Ordovician sandstones (and associated facies), southwestern Ontario (Report). Geological Survey of Canada. doi: 10.4095/288671. Open File 6856.
- ^ A, Uribe; Dario, Ruben (1994). "Petrography and Diagenesis of the Upper Cambrian Mt. Simon Sandstone, Southeastern Minnesota". Southeastern Minnesota.
- ^ a b A, Uribe; Dario, Ruben (1994). "Petrography and Diagenesis of the Upper Cambrian Mt. Simon Sandstone, Southeastern Minnesota". Southeastern Minnesota.
- ^ a b Lovell, Thomas R.; Bowen, Brenda B. (2013). "Fluctuations in Sedimentary Provenance of the Upper Cambrian Mount Simon Sandstone, Illinois Basin, United States". The Journal of Geology. 121 (2): 129–154. doi: 10.1086/669230. ISSN 0022-1376.
- ^ A, Uribe; Dario, Ruben (1994). "Petrography and Diagenesis of the Upper Cambrian Mt. Simon Sandstone, Southeastern Minnesota". Southeastern Minnesota.
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